Ring size in oversized piston?

[Sailman 1,291]

Been in contact with a small engine shop near me to consider his help in getting the K-161 on my 701 running. It appears to have a broken rod as piston does not move when rotating the drive pulley. Trying to gauge if this guy is capable for some of the repair (been in business a long time) and in discussing a possible over sized piston (if the measurements require that) he states you have to have .15 over rings to correctly seal a .10 over piston. Have not heard this before. What say you experienced engine re-builders out there?

He also said you do not turn down a crank shaft on the K series. It is much harder (cast iron) than the aluminum rod and should not need to be ground down and have undersized rod. Any wear should be on the rod connection. Again...what say you re-builders out there?

Trying to get an assessment of whether he is a good option to do some of the internals as needed. He has worked on them years ago.

[Rick3478 428]

15 minutes ago, Sailman said:

he states you have to have .15 over rings to correctly seal a .10 over piston.

 

He also said you do not turn down a crank shaft on the K series. It is much harder (cast iron) than the aluminum rod and should not need to be ground down and have undersized rod. Any wear should be on the rod connection

 

I say BS.

 

The only reason I can think of to use extra oversize rings is if you are trying to file them to an extra tight gap.  If you do that, you run the risk of heat expansion seizing the rings in the bore.  Don't ask how I know.  The parts are what they say they are.

 

Crank will depend on inspection when you get it apart.  If it's clean and shiny you might be able to use it as is.  In my experience, the thing that usually breaks rods is that it galls up and seizes.  There's a reason they make .010 under rods and sometimes even that is not enough.

 

Find someone who doesn't think he knows better than the manufacturer.

[Achto 27,565]

54 minutes ago, Sailman said:

he states you have to have .15 over rings to correctly seal a .10 over piston. Have not heard this before. What say you experienced engine re-builders out there?

He also said you do not turn down a crank shaft on the K series. It is much harder (cast iron) than the aluminum rod and should not need to be ground down and have undersized rod. Any wear should be on the rod connection.

 

I have used .010 over rings in a stock bore IF the bore is at the outer limits of wear BUT is still strait and true with in specs. This allows you to get a better seal. If you need to over bore the cylinder, the correct rings will come with your new oversized piston. Unless you go with OEM parts, then you may have to buy the piston & rings separate.

 

The rod is softer than the crank, this part is true. But I have measured many of crank shafts that were warn down, out of round or tapper. The only way to fix this issue is to turn the crank down.

 

Wish you lived close to me, I'd hook you up with a guy who won't try to blow smoke up your rear.

 

Maybe try @richmondred01 to see can do for you?

Edited February 6 by Achto

[rmaynard 15,434]

your engine guy does not know what he is talking about. I'd move on to a different shop. The K161 in a 701 is an older style with a standard bore of 2-7/8". I had my 701's K161 bored from old bore to new standard bore of 2-15/16". The new piston and rings installed were the "new" standard size for a K161/K181.

Also, even though my crank and connecting rod weren't damaged, the crank pin was out of round. I had it ground to .010 under, and replaced the rod with the same.

Edited February 6 by rmaynard

[ebinmaine 67,424]

I'm just going to go ahead and throw another NO vote. 

 

I wouldn't trust that person to hone down a broomstick I didn't care about.

[Pullstart 62,834]

17 minutes ago, ebinmaine said:

I wouldn't trust that person to hone down a broomstick I didn't care about.

Would you mind explaining how to do that to one you do care about?  

[Achto 27,565]

@Sailman This shop does not look to be all that far from you. Might be worth checking out. Looks like they can take care of boring the cylinder and turning the crank.

 

https://bradsautomachine.com/services

 

This is how I work with my machinist.

1 - I measure every thing to see what I will require for parts.

If you do not have a way to measure your parts, take them to the machine shop a long with the Kohler spec sheet & let them measure them for you.

2 - I take my new parts to the shop along with a copy of the Kohler spec sheet. This way they can fit the new parts to the tolerances given by Kohler.

 

 

Edited February 6 by Achto

[ebinmaine 67,424]

7 minutes ago, Pullstart said:

Would you mind explaining how to do that to one you do care about?  

 

 

If'n I gotta  'splainitt you prolly don'  want th' answer.  

[kpinnc 12,005]

1 hour ago, Sailman said:

Trying to get an assessment of whether he is a good option to do some of the internals as needed.

 

The last time I had engine work done, I saw the Kohler spec sheet on the wall in the office of the shop I was using. When I asked questions, the guy immediately went to the sheet for answers. If your guy doesn't have a copy, he should appreciate you getting it for him. If he doesn't, keep looking for an engine builder. 

 

"Rules" that a builder clings to (.015 ring stuff) with a water-cooled V8 build do not necessarily translate correctly to these air-cooled blocks. They get hot! 

Edited February 6 by kpinnc

[ri702bill 8,316]

1 hour ago, rmaynard said:

your engine guy does not know what he is talking about. I'd move on to a different shop. The K161 in a 701 is an older style with a standard bore of 2-7/8". I had my 701's K161 bored from old bore to new standard bore of 2-15/16". The new piston and rings installed were the "new" standard size for a K161/K181.

Also, even though my crank and connecting rod weren't damaged, the crank pin was out of round. I had it ground to .010 under, and replaced the rod with the same.

Oversized pistons and rings MAY not still be available for the small bore 701 and 702 K161 engines. Best to have it bored to the later 2-15/16 dimension - those parts are available.

Sounds like your local guy just does not want to bother cutting the crank journal - too bad - for him. Get your new parts FIRST before any machining, so the yet TBD shop can cut or bore accordingly to provide the best fit and clearances.....

[Achto 27,565]

26 minutes ago, ri702bill said:

Best to have it bored to the later 2-15/16 dimension - those parts are available.

Page 1.6 has all of the info that your machinist will need. I usually print this page & take it along to the machinist with my new parts.

https://resources.kohler.com/power/kohler/enginesUS/pdf/tp_2379.pdf

 

This is a very good source for parts. I have had very good luck with this seller. Measure or get things measured so you know what you need. Read through all of his instructions so that you order the correct parts.

https://www.ebay.com/itm/143655761198?hash=item21728cf52e:g:RUMAAOSwMRtek66Z&amdata=enc%3AAQAIAAAA0MFDQnYz8aI7e50TlWY9EmA%2FU0ICDAg8wfPBe4FDGLdWLCEjy0yxEapnyQNX7E8rDfCz8T%2FsuAqlEOajDHyqTBn7F8rAHhoQHLmfJI481EY4poB7sFzhE8MSvjVboCxuH57Ug6nZVN4xNbSUyfUML7e3p8FTHaoId90ZskJKtdOKd0jwfpk6G9GHlv%2FkuUTbeay%2BylowqRcHHVQJwtH7nA1vt9mdNafaOJwfcnjQgnYkdGvmSeKrL9z043G3lJWy2snLB5j0I9qA75XKGZSygZM%3D|tkp%3ABk9SR4bct_SvYw

 

[WHX?? 48,814]

2 hours ago, ri702bill said:

Oversized pistons and rings MAY not still be available for the small bore 701 and 702 K161 engines. 

They are available yet. Not in after market tho just NOS Kohler so abit more $$. Yes just go to 15/16 if it needs a new bore. Parts more available for the bigger bore. 

Doing a K161 now just inside 2 7/8 spec so can get rings in in std or .010 with some end gap work and a hone job. 

Saves the expense for a bore and don't have to pull the whole motor apart. 

Edited February 6 by WHX??

[squonk 41,068]

If the shop @Achto gave you doesn't pan out , contact @richmondred01

[Sailman 1,291]

7 hours ago, Achto said:

@Sailman This shop does not look to be all that far from you. Might be worth checking out. Looks like they can take care of boring the cylinder and turning the crank.

 

https://bradsautomachine.com/services

 

The shop I was talking to recommended this shop for the actual possible bore and crank work. I was hoping to get some help with the tear down and reinstall from the guy I contacted as I am unsure of my abilities in that department. I will check and see if Bradsautomachine does any of that. I checked with @richmondred01 but he no longer rebuilds K-161.

[Sailman 1,291]

Any suggestions on the possibility to open up the bottom, remove the head and see what the issue is with the rod? Possibly remove it and the piston and if no damage to cylinder wall I could take it to Brads and have the crank and cylinder checked. Maybe just replace the rod and piston if it was in spec? I will have the carb and starter off. Is that even possible without a complete tear down?

[Achto 27,565]

3 minutes ago, Sailman said:

Possibly remove it and the piston and if no damage to cylinder wall I could take it to Brads and have the crank and cylinder checked. Maybe just replace the rod and piston if it was in spec?

 

If you remove the piston from the cylinder, then you will at the very least have to get the cylinder ball honed to put new cross hatch in it and replace the rings.

 

The manual that I posted for you does a very good job of walking you through the disassembly and reassembly of the engine. Removing the oil pan is just 4 bolts, this simple task will let you see what happened to the crank. Post pics when you find the damage please.

 

Special tools needed to work on your engine.

Feeler gauge

torque wrench

ring compressor - a wide hose camp will work in place of this

valve spring compressor - can be done without but this makes the job easier.

 

Plus you have the total support of your family here on the forum. 

[richmondred01 2,237]

42 minutes ago, Sailman said:

The shop I was talking to recommended this shop for the actual possible bore and crank work. I was hoping to get some help with the tear down and reinstall from the guy I contacted as I am unsure of my abilities in that department. I will check and see if Bradsautomachine does any of that. I checked with @richmondred01 but he no longer rebuilds K-161.

My fingers aren’t able to do the two part cam anymore. I can certainly can have the machine work done. Grind the crank, bore the cylinder ream new guides and cut the valve seats. PM me for details. 
 

[WHX?? 48,814]

Sounds like you have a ton of options. Tell you what if your not comfortable doing it yourself box it up and send it to one of us. Very few working small engine guys I trust these days. They are just not into saving vintage steel. 

I know I would do it for free. Just parts & machine work. PM me if interested. 

[ebinmaine 67,424]

8 minutes ago, WHX?? said:

Sounds like you have a ton of options. Tell you what if your not comfortable doing it yourself box it up and send it to one of us. Very few working small engine guys I trust these days. They are just not into saving vintage steel. 

I know I would do it for free. Just parts & machine work. PM me if interested. 

 

 

You're a good man Jim. 

I won't say anything bad about you for at least 15 minutes.  

[wallfish 16,994]

Just now, ebinmaine said:

 

 

You're a good man Jim. 

I won't say anything bad about you for at least 15 minutes.  

I couldn't wait that long! LOL

Achto wrote  "Wish you lived close to me, I'd hook you up with a guy who won't try to blow smoke up your rear."

Jim just does sunshine! No smoke

[WHX?? 48,814]

It's just what I enjoy doing in retirement EB. Keeps me out of the tavern. Only problem is I question my choices 40 years ago ... shoulda opened a power shop rather than HVAC. 

Edited February 7 by WHX??
Speeling

[Achto 27,565]

20 minutes ago, WHX?? said:

shoulda opened a power shop rather than HVAC

 

Then your hobby would be playing with HVAC instead of tractors. 

[squonk 41,068]

He'd be driving 6 hrs. Across state lines to pick up a used Goodman furnace.

[RED-Z06 2,221]

When i used to do K series rebuilds, id bore it to +0.009" on the machine, then use a rigid 2 stone hone to bring it out..using the piston and rings to get my piston clearance, once i had piston clearance in spec, drop the rings in..check gaps, if they are too snug, open then up on a ring filer.

 

Alot of shops just rebuild by measuring then check ring gaps, they dont check thrust face clearance of the actual piston...you end up too snug or too loose.  Once im happy with my clearances i run the 3 stone to set crosshatch.  

 

It all centers around piston tolerances though, rings you can file down, bore you can open up..but piston isn't so simple to resize.

[Sailman 1,291]

Wow, the response has been amazing...what a great community! @WHX?? what a generous offer. I will plan to pull the engine when it warms up a bit here and like @Achto said see what I have got to deal with. If there is no damage other than the broken rod I will take it to the local machine shop to check the bore and crank shaft. If they are in spec I will have them do the cylinder work and can probably install the piston and rod myself. If the engine is worn out of spec I will be reaching out and take advantage of the offers here!

I rescued this 'ol 701 with hopes of restoring it to running condition. I probably could handle a tear down and rebuild as I have the tools but I just don't have a good dedicated space to keep things. Thanks again for all the good advice.

This one will make you chuckle...the small engine guy I mentioned stated that he was told by the EPA to punch a hole in any worn out Kohler K engine.....reason being they were so "dirty" the EPA did not want them rebuilt......hope I don't trigger any heart attacks!

 

Edited February 7 by Sailman